Add myCode and addressNone to stdlib

[Shvandre]

I think that two important functions are missing.

asm fun myCode(): Cell { MYCODE }

asm fun emptyAddress(): Address { b{00} PUSHSLICE }

Here is possible implementation. Maybe emptyAddress() should me named addressNone() ? because it is addr_none in block.tlb

[anton-trunov]

Maybe emptyAddress() should me named addressNone() ? because it is addr_none in block.tlb

yeah, addressNone sounds better to me

[Gusarich]

@anton-trunov @Shvandre myCode is already added in #986

[anton-trunov]

@Gusarich maybe let's add addressNone there as well and mark that PR as closing this issue too?

[novusnota]

Partially resolved in #986 — myCode() was added, but addressNone() was not.

Intermediate implementation of the latter looked like this:

asm fun addressNone(): Address? { b{00} PUSHSLICE }

Prior discussion: #986 (comment)

[anton-trunov]

@Gusarich Can we add addressNone now (notice there is no optional type here)?

asm fun addressNone(): Address { b{00} PUSHSLICE }

[anton-trunov]

Adding addressNone() should be part of #1119